> Is there a list of the signers, contributors, opponents etc. of the Magna
> Charta...where might it be found? ...

A fine book on *all* those involved with the Magna Carta is by Robert
Edwin Bye, _Magna Charta: King John and the Barons_ (Bridgeport, PA:
Chancellor Press, for the Baronial Order of Magna Charta, 1966). It has
biographical and (reasonably discriminating, but not 100% accurate)
genealogical sketches on King John, the advisers (some of them, like
William Marshall, who were essentially mediators), and the sureties (the
25 persons chosen by the barons to be the king's watchdogs, whose role is
discussed in clause 61 but who are not named in the charter itself). It
is these 25, misguidedly hailed by antiquarians, lawyers and genealogists
from the 17th century to the early 20th century as champions of 'liberty'
and opponents of tyranny, who are the qualifying ancestors for the various
hereditary Magna Carta societies, at least in this country. The best book
explaining the Magna Carta in its historical context is J. C. Holt's
_Magna Carta_, 2d ed. (Cambridge University Press, 1992; 1st ed. 1965);
he also edited an interesting short book on the interpretation and
mis-interpretation of the MC in subsequent eras: _Magna Carta and the Idea
of Liberty (New York, 1972; reprinted Malabar, FL: Krieger, 1982).

The 25 baronial-party sureties from the June 1215 charter are not named in
the charter; they are only known from 4 extant later lists, but there is
no disagreement about them. They were listed in order of importance or
social standing as follows (Bye, p. 37; Holt, appendix 8, pp. 478-80):

1. Richard de Clare, Earl of Hertford (known as Earl of Clare)
2. William de Fortibus, Earl of Aumale*
3. Geoffrey de Mandeville, Earl of Gloucester and Essex*
4. Saher de Quincy, Earl of Winchester
5. Henry de Bohun, Earl of Hereford
6. Roger Bigod, Earl of Norfolk and Suffolk
7. Robert de Vere, Earl of Oxford
8. William Marshall (the younger, later Earl of Pembroke)*
9. Robert Fitz Walter of Dunmow (leader of the baronial opposition party)
10. Gilbert de Clare (son of 1, later Earl of Hertford and Gloucester)
11. Eustace de Vesci*
12. Hugh Bigod (son of 6, later Earl of Norfolk and Suffolk)
13. William de Mowbray
14. the Mayor of London (ex officio: Serle Mercer was mayor in June 1215;
William Hardell in 1215/16--descendants not traceable)
15. William de Lanvallei
16. Robert de Ros (or Roos)
17. John de Lacy, Constable of Chester, later Earl of Lincoln
18. Richard de Percy*
19. John Fitz Robert [de Clavering / d'Evers]
20. William Malet
21. Geoffrey de Say
22. Roger de Montbegon*
23. William de Huntingfield
24. Richard de Montfichet*
25. William d'Aubigny of Belvoir